Update Vitess maintainers

[deepthi]

Removing vmg who is stepping down.
Ref: vitessio/vitess#18388

Pre-submission checklist for maintainer updates (delete this if you're updating a different file)

If you're adding a new maintainer to the CSV file, please review each of these actions as well:

• You've also sent an email with the addresses to cncf-maintainer-changes@cncf.io for access to Service Desk and mailing lists.
• The maintainer has also created or updated their LFX Individual Dashboard profile.
• Optional: You've also sent a PR with affiliation updates to cncf/gitdm.

[krook]

Thanks @deepthi. @vmg has been removed from our records, Service Desk, and lists.cncf.io.